The present invention relates to a medical occlusion clip and more particularly to an occlusion clip suited for sexual sterilization and adapted to be used on a fallopian tube.
Female sterilization, a medical procedure, is accomplished by occluding the fallopian tubes, which stops the egg from being delivered from the ovary to the uterus. Several techniques have been employed for such sterilization which is generally referred to as tubal ligation. One method involves bending the fallopian tube into a knuckle shape and tying a suture about the knuckle to obviate the passage of the egg. Another technique involves cutting the fallopian tube with a mono-polar or bipolar electrocautery and then cauterizing the ends of the tube. Yet another method requires placing a clip over the fallopian tube, the clip serving as a clamp to occlude the fallopian tube and prevent the passage of eggs through the tube.
Tubal ligation may be performed either by an open incision giving access to the fallopian tubes or by laparoscopic intervention which gives access to the fallopian tubes through a small cannula after the female's lower abdominal cavity has been insufflated using a gas such as CO2. The open technique is often used in conjunction with other open procedures such as a Caesarean section for childbirth. In open procedures, ligation can be accomplished effectively using either electrocautery or suture techniques because the working space is adequate to accomplish these procedures. In laparoscopic procedures, however, surgeons are generally limited to either electrocautery or the use of ligation clips.
Ligation clips have generally been of two types. The first type, exemplified by the clips disclosed in U.S. Pat. No. 4,325,377 ('377 Patent) have a latching mechanism that keeps the clip closed once it is clamped around a tube. The clip of the '377 Patent, typically referred to as a “Hulka clip,” has two clamping arms with an elastic band at the proximal end of the two arms. The clip is placed around the fallopian tube and then latched about the tube such that the clamping arms occlude the fallopian tube. Another clip of this type, known as a “Filshie clip,” is described in U.S. Pat. No. 5,575,802. The Filshie clip is a complex device constructed of two metal arms, a hinge, a latch and a silicon liner covering the two metal arms. The silicone liner gives some degree of resiliency to the clip. The Filshie clip is placed about the fallopian tube and closed by rotating one arm about the hinge point. To latch the clip, one arm is bent by applicator pressure and is engaged by the latch mechanism. The silicon liner compresses the fallopian tube, to a degree dictated by the applicator pressure.
Clips of this type have inherent deficiencies. The Filshie clip, for example, is overly complex, being made of two separate arms, a hinge, a latch and a silicon liner. In addition, the applicator for the Filshie clip must be periodically calibrated to insure proper fallopian tube occlusion pressure.
Both the Filshie and Hulka clips are designed so that the clips must be inserted into the body cavity in a, more or less, open configuration. For laparoscopic procedures this means that the cannula through which the clip is inserted must be large because the clip is in a high profile (i.e., open) state. Typically, the trocar port diameter requirement is from 8 mm to 12 mm depending on the technique used to install the clip. Trocar ports of this size require the procedure to be done in a hospital or similar clinical setting so that general anesthesia is administered to the patient. The added anesthesia cost and facility cost often make the total cost prohibitive. In addition, an 8-12 mm trocar entry wound requires that both the fascia and the skin layers be closed with sutures following the procedure to protect the patient from a postoperative hernia developing.
Another deficiency of the Hulka and Filshie clips is that neither occludes the fallopian tube in more than one place. In addition, the cost of the clips is such that redundancy is not economically practical. This lack of redundancy increases the likelihood of an occlusion failure which can result in an undesired pregnancy. Also, these clips require the use of a reusable single fire applicator.
The second type of clip may be referred to as a “spring clip” and involves the use of a biasing force rather than a latch to maintain a clamping force on the tube. An example of this type of clip is described in U.S. Pat. No. 6,350,269 ('269 Patent). This clip uses a coil spring to bias a clamping arm to clamp a vessel between the clamping arm and a support member. The clip is used in general surgery for occluding vessels and ducts such as the cystic artery and the cystic duct.
The spring clip of the '269 Patent is not suitable for occluding fallopian tubes for a number of reasons. The construction of the bias coils is such that the biasing force decreases as the vas becomes smaller, which often occurs in postpartum fallopian tubes. In addition, the single clamping arm described in the '269 patent is not placed symmetrically with respect to the arms of the support member. As a result, the clip of the '269 Patent does not provide equal occlusion on each side of the clip. Also, the open end of the clamping arm provides a surface that can become snagged on tissue and cause damage.
In general, there are numerous problems associated with the clips that have heretofore been used for tubal ligation. These problems have resulted in a significant failure rate that is attributable to a variety of failure modes. These include failure to maintain an acceptable occlusion force on the tube over time, misapplication by the surgeon, failure of the applicator to apply the proper pressure, and failures due to the complex structure of the clip itself.
Previous clip designs also have limitations with respect to reversibility. Although tubal ligation is generally considered to be a permanent procedure, a growing number of fertility doctors have undertaken procedures for reversing sterilization. As a general matter, the smaller the footprint (i.e., the area affected) of the clip on the fallopian tube, the more likely it will be that a successful reversal of the ligation procedure may be accomplished.